The sensor is S1 in this alarm that we found in a Radio Electronics magazine from May 1971. Several sensors can be used in series. The SCR supports equivalents from the 106 series.
This circuit is from 1990 documentation. When we press D1 the lamp remains on for a time interval that...
This 1995 circuit uses interruption sensors or NC connected in series in any quantity. With the...
This circuit from a Radio Electronics magazine from June 1969 already shows the use of the newly...